We had a similar talk while moving from kde3 to kde4 (aka qt3 to qt4). gtk2 will slowly fade out of the archive, so a goal would be to have a gtk2 free distro. As GTK world is big this needs quiet a bit of time. Python is a (bit) smaller universe and has the very same "problem": Moving from python2 to python3 …

In unstable you will always be in the middle of at least one transition, more likely a million. Some more visible than others …

P.S.: oldstable doesn't really help, it is updated too every once in a while …

_________________MfG. DonKult
"I never make stupid mistakes. Only very, very clever ones." ~ The Doctor